μBrowser

The fastest, cheapest browser automation for Claude.

μBrowser      ██████ 51s  $0.18
Dev Browser   ████████████████████████████████████████ 3m 53s  $0.88
Playwright    ████████████████████████████████████████████████ 4m 31s  $1.45

Benchmarks

Tested on dev-browser-eval game-tracker task with Claude Opus 4.5 (benchmark setup cloned from SawyerHood, eval tasks created independently):

Method	Time	Cost	Turns
μBrowser	51s	$0.18	7
Dev Browser	3m 53s	$0.88	29
Playwright MCP	4m 31s	$1.45	51

Results:

• 5× faster than Dev Browser
• 5× cheaper than Dev Browser
• 8× cheaper than Playwright MCP

Latest local run (dev-browser-eval simulation, HN proxy):

Method	Time	Cost	Turns	Tokens
Traditional (6 calls)	17.36s	$0.1439	6	2177
μBrowser (batch)	6.87s	$0.0052	1	204

How It Works

1. Batch Execution

Combine 25+ browser actions into a single API call:

{"steps": [
  {"tool": "navigate", "args": {"url": "/login"}},
  {"tool": "type", "args": {"selector": "#email", "text": "user@test.com"}},
  {"tool": "type", "args": {"selector": "#pass", "text": "secret"}},
  {"tool": "click", "args": {"selector": "button[type=submit]"}}
], "snapshot": {"when": "final", "maxElements": 40}}

Others make 4 separate calls. We make 1. 75% fewer API calls.

2. Ultra-Compact Snapshot Format

Standard HTML (~180 tokens):

<button id="e1" role="button">Submit</button>
<input id="e2" type="email" placeholder="Email" required>
<input id="e3" type="password" placeholder="Password">

μBrowser (~50 tokens):

btn#e1"Submit"
inp#e2@e~"Email"!r
inp#e3@p~"Password"

70% smaller snapshots. Output tokens cost 5× more than input.

3. Minimal Responses

{"ok":true}
{"ok":true,"snap":"btn#e1\"Submit\"\ninp#e2@e~\"Email\""}

Only return DOM when explicitly requested.

Speed + Cost Tuning

Environment variables:

• UBROWSER_BLOCK_STYLESHEETS=1 blocks CSS for faster loads (may affect layout-dependent pages).
• UBROWSER_MAX_ELEMENTS=40 caps snapshots by default when maxElements is not provided.
• UBROWSER_PROFILE_DIR=~/.ubrowser/profile browser profile directory for session persistence.
• UBROWSER_CONSOLE_LIMIT=100 max console messages to retain in buffer.
• UBROWSER_NETWORK_LIMIT=100 max network requests to retain in buffer.

Snapshot options (per-call overrides):

• snapshot.maxElements limits returned elements for browser_snapshot, per-tool snapshots, and browser_batch.

Session Persistence

Browser state (cookies, localStorage, IndexedDB) persists to disk between MCP server restarts. This enables:

• Staying logged in across sessions
• Preserving form data and preferences
• Maintaining shopping carts and app state

Profile stored at ~/.ubrowser/profile by default (customize with UBROWSER_PROFILE_DIR).

Implementation Details

Pre-injected extraction script — Script is injected once and JIT-cached in browser, eliminating recompilation overhead. Subsequent snapshots complete in <1ms.

Batched visibility checks — All getBoundingClientRect() calls happen in a single pass, avoiding layout thrashing that occurs with per-element checks.